1. Field of the Invention
This invention relates to a disposable diaper for use of infants, incontinent persons, and adults.
2. Description of the Related Art
In general, a disposable diaper is of a flat type and usually comprises an elongated body including a liquid permeable topsheet, a liquid impermeable backsheet, and an absorbent member interposed between the topsheet and the backsheet. The elongated body has a stomach-side portion which is located on the stomach side of a diaper wearer when the diaper is worn, and a back-side portion which is located on the back side of the wearer when the diaper is worn.
Recently, there has been proposed a pull-on type disposable diaper in which a pair of leg opening portions and a single waist opening portion are formed by affixing the stomach-side portion to the back-side portion through a pair of side flaps which are formed on the body along its longitudinal sides (see Japanese Laid-Open Patent Application No. Sho 61-207605).
In the pull-on type disposable diaper above outlined, the pair of leg opening portions are expansible so that the diaper fits well to the body contour of the diaper wearer. Usually, the wearer puts on the diaper while standing. Therefore, this diaper is used as a toilet training device for encouraging the infant wearer to finish with a diaper (i.e., to be well without the diaper), or for the use of incontinent persons or adults who can walk.
Also, the above-mentioned pull-on type disposable diaper has, when compared with a so-called flat-type diaper, the features in the respect that the diaper wearer can pull it upwardly or downwardly by himself/herself just like a normal undergarment. However, in order for the diaper wearer to easily put on the diaper by himself/herself and not to allow the discharged materials to leak, an excellent fit is required for the pull-on type disposable diaper. Furthermore, compliance enough to follow the busy movements of the diaper wearer is required.
In order to fulfill these requirements, Japanese Laid-Open Patent Application No. Hei 2-4364 proposes a pull-on type disposable diaper in which side portions for affixing a stomach-side portion of a body to a back-side portion thereof are each provided with a side panel (side portion), and edge areas of the stomach and back-side portions of the body are provided with elastic members, respectively.
However, in the pull-on type disposable diaper proposed in the above-mentioned Laid-Open Patent Application No. Hei 2-4364, since the side panel is of a single member and each member has the same degree of expansive property, a tightening force must be increased in order to prevent the diaper from slipping down and in order to enhance the fit. This gives an undue sense of oppression to the diaper wearer and spoils the easiness at the time the diaper is put on and taken off. This further causes the sense of oppression to be concentrated on both sides of the wearer's waist portion to make the wearer's skin irritated.
Furthermore, since the stress mostly concentrates on the area around each leg of the diaper wearer by the side panel when the diaper is worn, the area around the wearer's waist portion is comparatively loosened and therefore, the diaper is liable to slip down as the wearer moves actively and due to the weight of the discharged materials. Since the crotch portion also becomes loosened, the discharged materials are liable to leak. In order to avoid the foregoing, another type of disposable diaper has been proposed having a gather in the crotch portion thereby preventing leakage. However, this disposable diaper actually has the shortcoming in that when the waist portion becomes comparatively loosened in accordance with busy movements of the infant diaper wearer, the diaper slips down to form a space between the diaper and its wearer and the body fluid tends to leak through this space.
Furthermore, the above-mentioned pull-on type disposable diaper having side panels has the shortcoming in that a baby wearer finds it comparatively difficult to put on. Also, in the conventional pull-on type disposable diaper, since the expansible member of the waist portion is provided only to the waist opening portion, a gather, which is formed by the expansible member, is not continuously connected to side panel and therefore, a space is occasionally formed between the waist portion of the diaper and its wearer. Accordingly, it has the shortcoming in that the expansible member fails to expand or contract sufficiently, and the diaper fails to fit well to the wearer around his/her body, thereby allowing the discharged materials to leak through the space formed between the diaper and its wearer, and allow the diaper to slip down as a result of a decrease in a degree of compliance to the busy movements of the wearer.